ADOBE AFTER EFFECTS 7.0
User Guide
508
Wall controls for Particle Playground (Pro only)
Wall controls contain particles, limiting the area within which particles can move. A wall is a closed mask that you
create by using a mask tool, such as the Pen tool. When a particle hits the wall, it bounces off at a velocity based on
the force with which it hit.
Boundary Specifies the mask to use as the wall. You can create a new mask by drawing one on the effect layer.
Affects controls for Particle Playground (Pro only)
Many Particle Playground controls include Affects controls. Affects controls specify which particles are affected by
the encompassing control. For example, the Affects controls within the Particle Exploder controls specify which
particles the Particle Exploder affects.
Particles From Specifies the particle generator or combination of particle generators whose particles you want affect.
Selection Map Specifies the layer map that influences which particles are affected. (See “Replacing default particles
with layers using Layer Map (Pro only)” on page 504.)
Note: The simulation space is not bounded by the dimensions of the layer to which Particle Playground is applied. You
may need to use a selection map that is larger than the Particle Playground layer so that dots that are not visible are still
affected by Selection Map.
Characters Specifies the characters you want to affect. This control applies only if you are using text characters as
the particle type.
Older/Younger Than Specifies the age threshold, in seconds, above or below which you want to affect a particle.
Positive values affect older particles, and negative values affect younger particles. For example, a value of 10 means
that as soon as a particle reaches 10 seconds, it changes to the new value.
Age Feather Specifies the age range in seconds within which the Older/Younger Than value is feathered, or softened.
Feathering creates a gradual, rather than abrupt, change. For example, if you set Older/Younger Than to 10 and Age
Feather to 4, about 20% of particles start changing when they’re 8 seconds old, 50% change when they’re 10 seconds
old (the Older/Younger Than value), and the remainder change by the time they’re 12 seconds old.
About Property Mappers and Particle Playground (Pro only)
You can control specific properties of individual particles by using a layer map and either the Persistent Property
Mapper or the Ephemeral Property Mapper. You can’t alter a specific particle directly, but you can use a layer map to
specify what happens to any particle that passes over a specific pixel in the layer. Particle Playground interprets the
brightness of each layer map pixel as a specific value. (See “Replacing default particles with layers using Layer Map
(Pro only)” on page 504.) The Property Mapper associates a specific layer map channel (Red, Green, or Blue) with a
specific property, so that as a particle passes over a certain pixel, the brightness value at that pixel modifies the
property.
A particle property can be modified in either a persistent or an ephemeral way:
• A persistent change to a particle property retains the most recent value set by a layer map for the remaining lifespan
of the particle, unless the particle is modified by another control such as Repel, Gravity, or Wall. For example, if
you use a layer map to modify particle size and you animate the layer map so it exits the frame, the particles keep
the last size value set by the layer map after it exits the frame.
• An ephemeral change to a particle property causes the property to revert to its original value after each frame. For
example, if you use a layer map to modify particle size and you animate the layer map so that it exits the frame,
eachparticlereturnstoitsoriginalsizevalueassoonasnolayermappixelscorrespondtoit.Similarly,ifyouapply
an operator such as Add, each time a particle passes over a different layer map pixel, the value of the layer map
pixel is added to the original value of the particle.
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